230 



NOTES ON A COLLECTION OF POLYPLACOPHORA FROM CARNARVON, 

 WESTERN AUSTRALIA, WITH DEFINITIONS OF A NEW GENUS AND 



TWO NEW SPECIES. 



By Edwin Ashby, F.L.S., M.B.O.U. 



[Read August 9, 1923.] 



Plates XVI. to XIX. 



I am indebted to Mr. Worsley C. Johnston, of Western Australia, for the 

 gift of one of the most remarkable collections, though small as to number of 

 species, of Polyplacophora ever made on the occasion of a single brief visit. 



It includes, amongst others, a small but new shell of a unique type that 

 requires the establishment of a new genus for its reception ; the rediscovery of 

 a f)articularly interesting form of Sclerochiton, that has only been known from a 

 single specimen, in the British Museum, and concerning which doubt has been 

 expressed as to whether it was of Australian origin ; and, finally, the rediscovery 

 of a strange form of Cryptoplax that has been only known from a single minute 

 specimen deposited in the Berlin Museum. 



The collection was made on the occasion of a brief visit to Carnarvon, 

 situated in Shark Bay, Western Australia. The entire absence of one of the 

 commonest shells of that State, Liolophura hirtosus, (Peron) Blainville, of 

 which I have specimens from as far north as the Abrolhos Islands, is char- 

 acteristic of the whole collection. All except two species are apparently tropical 

 forms. The absence of any representative of the genus Plaxiphora is the more 

 remarkable, because at Dongarra, 300 miles further to the south, I found them 

 living together with Onithochiton scholvieni, this latter being very numerous at 

 Carnarvon. 



ToNiciA (Lucilina) delecta, Thiele, 1914. 



PI. xviii., fig. 2. 



(Thiele, Fauna Sudwest Australiens, Polyplacophora, pp. 297, 298, 1911 ; Ashby, Trans. 

 Roy. Soc. of S. Austr., vol. xlv., p. 47, pi. vii., fig. 2 a, b, c.) 



Four specimens of this interesting shell were taken, and they are, I believe, 

 the first that have been found other than on pearl shell. 



As the complete shell has not hitherto been figured, I include a photograph. 



Onithochiton scholvieni, Thiele, 1910. 



Pi. xviii., fig. 1. 

 (Thiele, Rev. des Sys. der Chitonen, Zool., pt. 2, p. 99, pi. x, figs. 60, 61, 1910; Ashby, 

 I.e., p. 45.) 



. A very fine series of this beautiful Onithochiton were collected. Owing to 

 their perfect condition they reveal features in colour and sculpture that have 

 not before been noticed. As no figure of the complete shell has been published, 

 I include a photograph. 



ACANTHOPLEURA GEMMATA, Blainvillc, 1825. 



(Chiton gemmatus, Blain., Diet. Sc. Nat., xxxvi., p. 544, 1825 ; Ashby, Journ. and Proc. 

 Roy. Soc. W. Austr., vol. viii., p. 29, 1921.) 



Half a dozen juvenile, well-preserved specimens were secured of this species. 

 They are interesting in that the girdle in some of them is furnished with unusually 

 long spicules. 



